Uninterruptible power supplies, also known as uninterruptible power sources (UPS) are electrical apparatuses known in the art that provide emergency power to a load when the input power source, typically mains power, fails. A UPS differs from an auxiliary or emergency power system or standby generator in that it will provide near-instantaneous protection from input power interruptions, by supplying energy stored in batteries, supercapacitors, or flywheels. The on-battery runtime of most uninterruptible power sources is relatively short (only a few minutes) but sufficient to start a standby power source or properly shut down the protected equipment. A UPS is typically used to protect hardware such as industrial equipment, computers, data centers, telecommunication equipment or other electrical equipment where an unexpected power disruption could cause injuries, fatalities, serious business disruption or data loss. UPS units range in size from units designed to protect a single computer without a video monitor (around 200 volt-ampere rating) to large units powering entire data centers or buildings.
Rotary Flywheel UPS systems used in mission critical facilities provide very limited time to transition to back up generators after a power loss usually 15 to 45 seconds depending on the load. Theoretically, this “ride through” should be adequate to allow the backup generators to start. In the event that the backup generators fail to start, there is no time for an orderly shutdown of the systems. Costs associated with power failures are significant, and may collectively (billions of dollars annually). As an example, banks where millions of transactions are taking place every minute are exposed to significant losses during a power failure. Most mission critical facilities will install battery backup in order to provide adequate time for orderly shutdowns and to ensure that there is adequate time to get the backup generators started. Battery backup used to provide power to critical systems for an extended period of time is often expensive, requires dedicated space with special ventilation and fire protection systems, requires maintenance and is environmentally unfriendly among other things. Additionally, circumstances may occur where the ride through time in a rotary wheel UPS is not sufficient to allow backup batteries or generators to fully engage. In other instances, power outages may be brief enough where it becomes inefficient to engage in a backup battery/generator system, only to disengage a short time later. Accordingly, extending the run time (or ride through) of a rotary wheel UPS may provide advantageous benefits.